878-55-7Relevant academic research and scientific papers
Synthetic bicyclic analogues of quassinoids
Lang'at, Caroline C.,Watt, Robert A.,Toth, Istvan,Phillipson, J. David
, p. 6857 - 6866 (2007/10/03)
A series of simple bicyclic analogues of quassinoids have been prepared including compounds with ring A typical of bruceolides and dehydrobruceolides. The synthesis of bicyclic compound 5 and tricyclic analogue 6 was accomplished by acid catalysed Robinson Annelation reaction. Hydroxyketone 9a and its 2-substituted analogues were also prepared to study the structure activity relationship.
145. Stereochemistry of the Robinson Anellation: Studies on the Mode of Formation of the Intermediate Hydroxy Ketones
Nussbaumer, Cornelius
, p. 1621 - 1636 (2007/10/02)
The stereochemical outcome of the base-catalyzed cyclization of diketones 5-8 has been investigated under protic conditions (Scheme 3).The more stable trans-fused ketols are preferentially formed in kinetically controlled aldol reactions, when the incipie
Synthesis of (+/-)-Geosmin. Part 1. On the Synthesis and Epoxidation of 1,4a-Dimethyl-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one
Hansson, Lars,Carlson, Rolf,Sjoeberg, Anna-Lena
, p. 1036 - 1041 (2007/10/02)
An improved method for the preparation of 1,4a-dimethyl-4,4a,5,6,7,8-hexahydronaphthalene-2(3H)-one has been developed.This compound has been used as a key intermediate in several previous syntheses of geosmin.The regioselectivity in the alkylation of 2-methylcyclohexanone with ethyl vinyl ketone or 1-chloro-3-pentanone was investigated. The stereoselectivity in the epoxidation of the octalone by hydrogen peroxide, t-butyl hydroperoxide and m-chloroperbenzoic acid was also studied.The results obtained were, to some extent, different from previous reports, both with respect to regio- and stereo-selectivity.The isolated yield of the octalone was 81-83percent as a 96:4 mixture with the 1,8-dimethyl isomer.Epoxidation of this material using m-chloroperbenzoic acid resulted in a 92:8 (α:β) mixture of epoxides, which also contained 4percent of the epoxide(s) from the 1,8-dimethyloctalone isomer(s).The isolated yield of epoxide mixture was 89percent.
1,5-DICARBONYL COMPOUNDS A GENERAL PREPARATION METHOD
Duhamel, P.,Hennequin, L.,Poirier, J. M.,Tavel, G.,Vottero, C.
, p. 4777 - 4786 (2007/10/02)
In this report, a general method for the preparation of 1,5-dicarbonyl compounds and six membered ring annelation is described.This method involves the reaction of hemiacetal vinylogs 1 with enol ethers 2 or 3 in the presence of a Lewis acid.This reaction was successfully applied to the enol ethers of α and α,α'-hindered ketones such as 2,2,6-trimethyl cyclohexanone. α-Cyperone and 6-epi-α-cyperone were obtained using this process.
A Synthetic Approach to the Quassinoids
Heathcock, Clayton H.,Mahaim, Cyril,Schlecht, Matthew F.,Utawanit, Thanin
, p. 3264 - 3274 (2007/10/02)
A synthetic route to the quassinoids has been developed.Two-stage annelation of 2-methylcyclohexanone with 1-chloro-3-pentanone gives tricyclic dienone 9 (60percent), which is oxidized by acetyl chromate in acetic acid to give dienedione 27 (80percent).Bisketalization of this material followed by hydrolysis of the conjugated enone ketals provides monoketal 30 (77percent), along with recovered 27.Ring C of 30 is functionalized by the Stiles and Reich methods to obtain the unsaturated keto ester 33 (73percent).The latter material reacts with ketene acetal 35 at 5-6 kbar and room temperature to give an adduct that is desilylated by treatment with aqueous KF; keto diester 39 is produced in 95percent yield.Epoxidation of 39 occurs smoothly with m-CPBA to give 46 (88percent), which is converted into allylic alcohol 40 by the two-step Sharpless procedure (78percent).Finally, pyridinium chlorochromate induces solvolytic cyclization of 40, affording 41 in 55percent yield.In the course of the investigation, it was also discovered that β-keto ester 46 is oxidized by m-CPBA to 47 in quantitative yield.
ELECTROOXIDATIVE SIMULATION OF STEREOSELECTIVITY IN MICROSOMAL ALLYLIC HYDROXYLATION
Shono, Tatsuya
, p. 91 - 94 (2007/10/02)
A comparison of the stereochemistry of liver microsomal γ-hydroxylation of some cyclic α,β-unsaturated ketones with that of electrochemical γ-acetoxylation of the corresponding dienol esters and with that of peracid oxidation of the dienol esters has been carried out.
Stereoselective Total Synthesis of (+/-)-Isocostic and (+/-)-3-Oxoisocostic Acids
Cruz, Raymundo,Martinez, Rosa M.
, p. 451 - 456 (2007/10/02)
Stereoselective
Dienone-Phenol Rearrangements of Bicyclic Cyclohexa-2,5-dienones; Confirmation of a Multistage Mechanism
Waring, Anthony J.,Zaidi, Javid Hussain,Pilkington, James W.
, p. 1454 - 1459 (2007/10/02)
Two mechanisms are well established for the dienone-phenol rearrangements of bicyclic cyclohexadienones of the 4a-alkyl-5,6,7,8-tetrahydronaphthalen-2(4aH)-one type, of which the 4a-methyl compound (1) and the steroidal 1,4-dien-3-ones are examples.They involve, for (1), either a direct alkyl shift from C-4a to C-4 and deprotonation to give a 4-alkyl-5,6,7,8-tetrahydro-2-naphthol or a shift of the 4a,5-bond from C-4a to C-8a with formation of a spiran intermediate and further ring migration from C-8a to C-1 to form a 4-alkyl-5,6,7,8-tetrahydro-1-naphthol.A further mechanism, for which there was little strong evidence, involves an alkyl shift from one angular position, C-4a, to the other, C-8a, followed by further ring migrations via a spiran intermediate to give an additional route to the 4-alkyltetrahydro-2-naphthol product.The products of rearrangement of 3,4a- and 1,4a-dimethyl-5,6,7,8-tetrahydronaphthalen-2(4aH)-ones in aqueous sulphuric acid, and in acetic anhydride with sulphuric acid catalysis, have been studied critically.The use of quantitative 13C n.m.r. spectroscopy confirms the identity and ratios of products deduced using 1H n.m.r. spectroscopy and other techniques.The results show that the third, suspect, mechanism does indeed operate, and that it contributes significantly to the formation of 4-alkyltetrahydro-2-naphthol products from both dienones.
